1. Field of the Invention
The present invention relates to the fabrication of electronic circuit assemblies and, in particular, to a method of stacking of substrates having mounted components so as to increase surface component density in such assemblies.
2. Description of the Prior Art
The electronic components of many conventional electronic circuits are typically mounted on a substrate, such as a circuit board, which provides conductive paths by which the components are interconnected into the desired electronic circuit. The substrate may incorporate peripheral electrical connection points, or connector pins, to provide for electrically connecting the electronic circuit to a system circuit board.
Certain multi-lead electronic components, such as integrated circuits, can be vertically integrated, or stacked, with one or more other physically similar components to form an electronic module which can be mounted to the substrate. By stacking electronic components before mounting, it becomes possible to increase the number of such components electrically connected to the substrate without necessitating a corresponding increase in the surface area of the substrate.
However, the methods of stacking electronic components described in the relevant art often call for custom-designed components, special material or complex fixturing to achieve electrical interconnection between the layers of a multi-layer substrate. As can be appreciated by one skilled in the relevant art, custom materials, processes, and fixturing increase the cost of electronic circuit fabrication.
Moreover, most conventional stacking methods do not provide for the electrical testing of individual electronic components which form the stack. With a conventional stacking configuration, a stack is tested only when completely assembled. If failure results from an individual faulty component, the entire stack may be rejected if the repair of an assembled stack, if possible, is not cost effective.
The present state of the art indicates a need for an improved method of stacking electronic components into electronic circuit assemblies.
It is an object of the present invention to provide a module stacking configuration which improves yield and reduces cost by providing for the test and repair of each individual component in the module prior to installation of the module onto a circuit board.
It is a further object of the present invention to provide such a module which utilizes standard commercially available materials.
It is yet another object of the present invention to provide such a module which uses proven assembly techniques and fixtures.
It is still another object of the present invention to provide such a module which can be mounted so as to overly existing components of a circuit board.
Other objects of the invention will, in part, appear hereinafter and will, in part be apparent when the following detailed description is read in connection with the drawings.